An epoxy resin composition has excellent electric performance and adhesive strength. Therefore, it has been used for various electric fields and electronic fields in the past. In addition, in cases where only insufficient effects can be obtained even when a conventional epoxy resin is used alone or in mixture, cyanate ester-epoxy composite resin composition comprised of mixing epoxy resin with cyanate ester is often used as a thermally-resistant resin composition for sealing of semiconductors or molding etc.
In recent years, as uses for electronic parts increase, durability and productivity are required under severe environmental conditions more than ever before to realize much higher thermal resistance and much more superior curing properties than before. Furthermore, as electronic circuits used in the periphery of semiconductor are highly integrated or speeded up, organic materials having low-dielectric tangent (low tan δ) as well as low-dielectric constant are required.
In order to meet these demands, liquid epoxy resin compositions used for sealing semiconductors comprised of, for example, cyanate ester, epoxy resin, inorganic filler and dihydrazide compound etc. (Patent document 1) and an invention using an amine curing agent for a composite composition which contains cyanate ester and epoxy resin (Patent document 2) were proposed, and also lots of cyanate ester-epoxy composite resin compositions such as a thermosetting resin composition using a latent curing agent which contains imidazole component together with cyanate ester and epoxy resin (Patent document 3) were proposed. However, these compositions have not only low productivity due to long curing time, but also insufficient thermal resistance and can not satisfy the requirements of low-dielectric constant and low-dielectric tangent (low tan δ). Therefore, further improvement is required.